At times this was almost painful to watch. Here was an old warhorse being schooled by the fizzing man of the moment. Here was the past being undone by the present. It all came to a head in the 58th minute.

That was when Mo Salah chased after a ball in the middle of the Arsenal half and David Luiz attempted to dispossess him. As the centre back tried to move into position, the impulse was to shield the eyes. Luiz had already brought Salah down for a penalty with one of the most shameless pulls of the shirt you will ever see. And here he was, already booked, trying to corral a player whose pace across five metres...